Question

What is the trend of ionisation energy going from left to right along a period?

[1 mark]

• A. Increases
• B. Decreases
• C. Remains the same
• D. Increases and then decreases

Answer 1

The correct option is A Increases

As the atomic number increases as we move from left to right across a period, the effective nuclear charge also increases. Thus, the valence electrons experience a greater pull towards the nucleus. This results in a decrease in atomic radii. As a result, more energy is required to completely extract the valence electron. Hence, ionisation energy increases as we move across a period.